C++ copy()函数

墨蓝 2022-06-10 05:10 169阅读 0赞

function template

# std::copy #

template <class InputIterator, class OutputIterator>
      OutputIterator copy (InputIterator first, InputIterator last, OutputIterator result);

Copy range of elements

Copies the elements in the range  `[first,last)` into the range beginning at  result.  
  
The function returns an iterator to the end of the destination range (which points to the element following the last element copied).  
  
The ranges shall not overlap in such a way that  result points to an element in the range  \[first,last). For such cases, see  [copy\_backward][copy_backward].  
  
The behavior of this function template is equivalent to:

<table style="font-size:12px; color:black"> 
 <tbody> 
  <tr> 
   <td style="color:rgb(160,160,160); text-align:right; vertical-align:top; min-width:20px"> <pre style="margin-top:0px; margin-bottom:0px"><code>1
2
3
4
5
6
7
8
9
</code></pre> </td> 
   <td style="border:1px solid rgb(192,192,208); vertical-align:top; background:rgb(239,239,255)"> <pre style="margin-top:0px; margin-bottom:0px"><code>template&lt;class InputIterator, class OutputIterator&gt;
  OutputIterator copy (InputIterator first, InputIterator last, OutputIterator result)
{
  while (first!=last) {
    *result = *first;
    ++result; ++first;
  }
  return result;
}</code></pre> </td> 
  </tr> 
 </tbody> 
</table>

示例：

<table style="font-size:12px; color:black"> 
 <tbody> 
  <tr> 
   <td style="border:1px solid rgb(192,192,208); vertical-align:top; background:rgb(239,239,255)"> <pre style="margin-top:0px; margin-bottom:0px"><code><cite style="font-style:normal; color:rgb(0,112,0)">// copy algorithm example</cite>
#include &lt;iostream&gt; <cite style="font-style:normal; color:rgb(0,112,0)">// std::cout</cite>
#include &lt;algorithm&gt; <cite style="font-style:normal; color:rgb(0,112,0)">// std::copy</cite>
#include &lt;vector&gt; <cite style="font-style:normal; color:rgb(0,112,0)">// std::vector</cite>

int main () {
  int myints[]={10,20,30,40,50,60,70};
  std::vector&lt;int&gt; myvector (7);

std::copy ( myints, myints+7, myvector.begin() );

std::cout &lt;&lt; "myvector contains:";
  for (std::vector&lt;int&gt;::iterator it = myvector.begin(); it!=myvector.end(); ++it)
    std::cout &lt;&lt; ' ' &lt;&lt; *it;

std::cout &lt;&lt; '\n';

return 0;
}</code></pre> </td> 
   <td style="vertical-align:top; padding:0px">&nbsp;</td> 
  </tr> 
 </tbody> 
</table>

Output:

<table style="font-size:12px; color:black"> 
 <tbody> 
  <tr> 
   <td style="border:1px solid silver; vertical-align:top; background:rgb(231,231,231)"> <pre style="margin-top:0px; margin-bottom:0px">myvector contains: 10 20 30 40 50 60 70</pre> </td> 
  </tr> 
 </tbody> 
</table>

[copy_backward]: http://www.cplusplus.com/copy_backward